Abstract: Techniques for cache management may include: receiving pages of data having page scores, wherein each of the pages of data is associated with a corresponding one of the page scores, wherein the corresponding page score associated with a page of data is determined in accordance with one or more criteria including one or more of a deduplication score, a compression score, and a neighbor score that uses a popularity metric based on deduplication related criteria of neighboring pages of data; and storing the page of data in a cache in accordance with the plurality of page scores. The cache may include buckets of pages where each bucket is associated with a different page size and all pages in the bucket are the different page size. The one or more criteria may also include an access score. The page scores may be based on multiple criteria that is weighted.

Abstract: Techniques for data migration may include: copying data of a source logical device of a source system to a target logical device of a target system; during said copying, receiving at the target system an I/O operation directed to a logical address of the target logical device and intercepting the I/O operation on the target system; determining, on the target system, to request from the source system a data page stored at the logical address; responsive to determining to request the data page stored, performing processing including: issuing a request to the source system for the data page stored at the logical address; and responsive to receiving said request, sending information from the source system to the target system, wherein the information includes the data page stored at the logical address and additional logical addresses of the source logical device at which the data page is stored.

Abstract: An apparatus includes at least one processing device, with the at least one processing device being configured, in conjunction with synchronous replication of at least one logical storage volume between first and second storage systems arranged in an active-active configuration, to create a first snapshot of the logical storage volume in the first storage system, to create a second snapshot of the logical storage volume in the second storage system, to create a third snapshot of the logical storage volume in the first storage system, to initiate an asynchronous replication cycle to transfer differential data between the first and the third snapshots in the first storage system to the second storage system, and to utilize the second snapshot and the transferred differential data to create an additional snapshot of the logical storage volume in the second storage system that is synchronized with the third snapshot in the first storage system.

Abstract: An apparatus includes at least one processing device comprising a processor coupled to a memory, with the processing device being configured to maintain throughput statistics for at least portions of one or more asynchronous replication cycles of a replication process carried out between a first storage system and a second storage system, and to control a transition of the replication process from an asynchronous replication mode to a synchronous replication mode based at least in part on the maintained throughput statistics. The throughput statistics are illustratively updated in conjunction with each of a plurality of detected suspensions of the synchronous replication mode, and the asynchronous replication mode is reinitiated responsive to each of the detected suspensions of the synchronous replication mode. Other embodiments include methods and computer program products.

Abstract: An apparatus includes a processing device comprising a processor and a memory. The processing device is configured, in conjunction with synchronous replication of a logical storage volume between first and second storage systems, to receive a synchronous write request comprising at least a portion of a data page to be written to the storage volume, to determine a source processing module associated with the data page in the first storage system, to determine at least one of a process identifier and a processor identifier of the source processing module in the first storage system, and to select a particular one of multiple links between the first and second storage systems for use with the synchronous write request based at least in part on at least one of the process identifier and the processor identifier of the source processing module. The selected link is illustratively associated with a transmit processing module.

Abstract: An apparatus is configured to identify a storage volume to be added to a consistency group for replication from a source storage system (“source”) to a target storage system (“target”), to generate a snapshot of the storage volume, to create a dummy volume on the target, to copy the snapshot to the dummy volume, and to add the storage volume to the consistency group. In conjunction with replication of the consistency group from the source to the target, a determination is made for each of a plurality of data pages of the storage volume whether or not the data page already exists in the target as part of the dummy volume. For at least one data page that already exists in the target as part of the dummy volume, a reference count is incremented in the target for that data page instead of copying that data page from the source.

Abstract: Techniques for cache management may include: partitioning a cache into buckets of cache pages, wherein each bucket has an associated cache page size and each bucket includes cache pages of the associated cache page size for that bucket, wherein the cache includes compressed pages of data and uncompressed pages of data; and performing processing that stores a first page of data in the cache. The processing may include storing the first page of data in a first cache page of a selected bucket having a first associated cache page size determined in accordance with a first compressed size of the first page of data. The cache may be repartitioned among the buckets based on associated access frequencies of the buckets of cache pages.

Abstract: A storage system in one embodiment comprises a plurality of storage devices and a storage controller. The storage controller is configured to receive a delete instruction for a storage volume, and responsive to receipt of the delete instruction, to suspend any further changes to address metadata for the storage volume, to transfer the address metadata for the storage volume to persistent storage, and to delete the storage volume while also at least temporarily maintaining its data pages. The storage controller subsequently receives an undelete instruction for the deleted storage volume, and responsive to receipt of the undelete instruction, retrieves the address metadata from persistent storage and recovers the storage volume utilizing the address metadata. An expiration timer may be started in conjunction with the deletion of the storage volume, and responsive to the undelete instruction being received after a specified expiration time of the expiration timer, the undelete instruction is rejected.

Abstract: Host I/O requests directed to a logical storage volume are initially processed by accessing physical pages of non-volatile data storage having a default page size. An indication of an optimal page size for the logical storage volume is received, and the size of the physical pages of non-volatile data storage accessed to process host I/O requests directed to the logical storage volume is changed from the default page size to the optimal page size for the logical storage volume. The default page size is changed to the optimal page size for the logical storage volume by changing a size of physical pages of non-volatile data storage indicated by a mapping structure that maps logical addresses in an address space the logical storage volume to corresponding physical pages of non-volatile data storage from the default page size to the optimal page size for the logical storage volume.

Abstract: A system for optimizing page size associated with a snapshot tree associated with a storage array, where the system collects current page size information associated with the snapshot tree. The system determines an optimal page size for the snapshot tree. The system creates a new snapshot tree based on the snapshot tree, where the new snapshot tree comprises the optimal page size.

Abstract: An apparatus includes a processing device comprising a processor coupled to a memory, with the processing device being configured, in conjunction with synchronous replication of at least one logical storage volume between first and second storage systems, to acquire an address lock for a set of pages of the logical storage volume starting from a particular page of the logical storage volume, to determine content-based signatures for respective pages of the set of pages, to compute an additional signature as a function of the content-based signatures, and to send the additional signature and a pointer to the particular page from the first storage system to the second storage system, so as to permit the second storage system to verify consistency of the set of pages in the second storage system relative to the set of pages in the first storage system. Such operations are repeated for other sets of pages.

Abstract: An apparatus includes a processing device comprising a processor coupled to a memory. The processing device is configured, in conjunction with synchronous replication of at least one logical storage volume between first and second storage systems, to receive a synchronous write request comprising a data page to be written to the logical storage volume, to determine a content-based signature for the data page, and to send the content-based signature from the first storage system to the second storage system. Responsive to receipt in the first storage system of an indication from the second storage system that the data page having the content-based signature is not already present in the second storage system, the processing device is further configured to send the data page from the first storage system to the second storage system. The processing device in some embodiments implements a distributed storage controller of a content addressable storage system.

Abstract: A system, computer program product, and computer-executable method of providing a layout-independent cryptographic stamp of a distributed data set from a data storage system, the system, computer program product, and computer-executable method comprising receiving a request for a cryptographic stamp of the distributed data set, creating a hash of each slice of the distributed data set, and using each hash from each slice of the distribute data set to create the cryptographic stamp of the distributed data set.

Abstract: An apparatus includes a processing device comprising a processor coupled to a memory. The processing device is configured, in conjunction with synchronous replication of at least one logical storage volume between first and second storage systems, to receive a synchronous write request comprising a data page to be written to the logical storage volume, to determine a content-based signature for the data page, and to send the content-based signature from the first storage system to the second storage system. Responsive to receipt in the first storage system of an indication from the second storage system that the data page having the content-based signature is not already present in the second storage system, the processing device is further configured to send the data page from the first storage system to the second storage system. The processing device in some embodiments implements a distributed storage controller of a content addressable storage system.

Abstract: An aspect of performing rollback of a snapshot between source and target storage systems in an asynchronous replication session in which Sr? represents a remote snapshot subject to the rollback includes suspending host input/output operations to a current source volume (Vs), determining whether a snapshot (Sr) matching the snapshot Sr? is present in the source system and, upon determining the snapshot Sr is not present in the source storage system, searching a snapshot pair (Sk, Sk?) that is closest to the remote snapshot Sr?. An aspect also includes upon determining the pair Sk, Sk? is present in existing snapsets, performing a local rollback of the Vs to Sk, and performing remote rollback including applying a difference between Sk? and Sr? to the Vs via one of a snapshot differential bitmap from the target storage system between Sk? and Sr? for the Vs, and an internal reverse direction asynchronous replication cycle.

Abstract: A system, computer program product, and computer-executable method of providing remote snapshot access from a target site within a data storage system including a source site and the target site, the system, computer program product, and computer-executable method including receiving a request to replicate a snapshot from the source site to the target site, initializing replication of the snapshot, providing access to the replicated snapshot at the target site, and processing the replication of the snapshot to create a replicated snapshot.

Abstract: A method is used in host-based caching. A host receives a request for data, and identifies a host in a plurality of hosts that owns the data.

Abstract: Techniques for cache management may include: partitioning a cache into buckets of cache pages, wherein each bucket has an associated cache page size and each bucket includes cache pages of the associated cache page size for that bucket, wherein the cache includes compressed pages of data and uncompressed pages of data; and performing processing that stores a first page of data in the cache. The processing may include storing the first page of data in a first cache page of a selected bucket having a first associated cache page size determined in accordance with a first compressed size of the first page of data. The cache may be repartitioned among the buckets based on associated access frequencies of the buckets of cache pages.

Abstract: An apparatus is configured to generate a current snapshot set for a consistency group comprising a plurality of storage volumes subject to replication from a source storage system to a target storage system, to compare one or more configuration attributes of the current snapshot set to one or more configuration attributes of a previous snapshot set generated for the consistency group, to detect a change in at least one configuration attribute of the current snapshot set relative to the previous snapshot set based at least in part on the comparing, and to communicate the detected change in the configuration attribute from the source storage system to the target storage system so as to permit the target storage system to implement a corresponding configuration update for the consistency group. The generating, comparing, detecting and communicating are illustratively performed as part of an ongoing asynchronous or synchronous replication process carried out between the source and target storage systems.

Abstract: In one aspect, performance optimization for data persistency in asynchronous replication setups includes creating at a source site of a data replication system, a snapshot (snapshot N) of input/output (IO) requests as part of a replication cycle, computing a delta of snapshot N and a previously created snapshot (snapshot N?1), and transmitting the delta to a target site of the data replication storage system. An aspect further includes storing, at the target site, snapshot N?1 during transmission of the delta, and caching the delta to a non-persistent storage device. Upon determining an occurrence of a loss event at the target site, a further aspect includes transmitting, by the target site, a request to retransmit the delta, retransmitting, by the source site, the delta to the target site, caching the delta to the non-persistent storage device until successful transmission of the delta, and committing the transmitted delta to permanent storage.